The amp came in and it keeps cycling in and out of protection.
Idle current (at 12V) swings to 1-1.1A
It is a HIP4080 based amp and i have to say the quality of the pcb being a 3 layer design, is the best Korean i have ever seen.
Also the quality of the parts is also excellent, using ADs opamps.
Here are the readings in the 4080 chip :
5. cycling 4.7 to 5.9
email if you want the schematic
It appears that there is significant DC on the output (before the relay if the relay isn't engaging). If that's true and you have another 4080 on hand, I'd suggest replacing the one in the amp to see if it solves the problem. I'm assuming that you've checked all of the outputs and none were leaky or shorted.
Do not power the amp up with the 4080 out of the circuit unless you confirm that there are pull-down resistors on each of the outputs. On the schematic diagram, there are capacitors connected between gate and drain for each output but in the amp photos that I have here, those appear to be resistors. There may have been a mistake on the schematic diagram or they may have decided that it was better to have resistor there or... the capacitors in the amp look like resistors. The components in question are C69-C72.
removed the output fets and all 4 tested fine.
Put them back, mounted a new HIP4080 and the amp idles at 4-4.5A
Still no output.
Removed the fets again and one was shorted, so i am replacing all four now and i need a new 4080.
Will there be any issues if i buy the originals (HUF75639 in TO-247 case) ?
BTW there is no output relay on this amp.
Back here where the new parts finally arrived.
Replaced the output fets and installed pulldown resistors.
Now, without the 4080 chip mounted, but with the output fets on, i get the following readings at the socket :
6. a 125KHz triangle 7.78Vp-p
7. 100Hz square wave of 15V p-p (this is what i feed the amp with)
but it begins to distort when i drive a very strong input signal to the amp
Due to bad experience with this chip in the past, i need to know if its ok to use a new 4080 now.
I confirm there are 1n capacitors to the gates of the fets both in the amp in front of me and to the schematic i have
Finally i put the 4080 in the socket and the amp seems to work ok.
However, when i test drive it with a resistive load i notice that one side clips
prematurely (first pic), and if i load it with a 2 ohm load in hard clipping (pic2)
something seems wrong...is that normal?
How does the gate drive signal for the low-side FETs on the good half of the amp compare to those on the distorted half of the amp?
here are some pics
output power is around 500w, load is 2 ohm
it seems the turn on time is not very fast, could this overheat the fets ?
finally the amp does not make 700w at 2 ohm, the last pic shows the output at
500w. at this power level the rail voltage is very stable at around 68VDC
If the square wave that's swinging from rail to rail is square, the FETs are being switched on quickly enough to prevent heating.
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